Epoxy secured web collar

ABSTRACT

Embodiments of the invention include an apparatus, an assembly, and a kit for securing a web collar to a tubular member. According to one embodiment, a sleeve has a plurality of apertures selectively sized and spaced to form a web collar. The web collar is positioned on a segment of casing and is secured in place with set screws. Epoxy is disposed into the apertures and cured. The cured epoxy deposits on the casing are analogous to keys welded to a shaft, extending outwardly into the apertures to secure the web collar and the centralizer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a stop collar for use with a centralizer on a tubular member. More particularly, the invention relates to an improved method to secure a stop collar on a tubular member.

2. Description of the Related Art

Casing is a tubular member generally used to line a drilled earthen borehole to prevent collapse and to isolate the penetrated geologic formations. A joint of casing is typically about 36 to 44 feet in length, and has threaded connections at each end to facilitate coupling to adjacent joints of casing to form an elongated casing string. Casing strings are “made up” as they are run into the borehole, whereby consecutive segments of casing are threadably coupled to the proximal end of the casing string as the casing string is lowered into the borehole. After the desired length of casing string is inserted, the casing string is cemented into the borehole. A cement slurry is pumped from the surface down through the bore of the casing string and displaced from the distal end of the casing string into the annulus between the casing string and the borehole.

It is important that the casing string be positioned as closely as possible to the center of the borehole prior to introducing the cement slurry. Properly centering the casing string promotes uniform circumferential placement of the cement slurry around the casing string. Uniform placement of cement optimally reinforces the casing string, isolates the casing from corrosive formation fluids, and prevents unwanted fluid flow between penetrated geologic formations. Centralizers of various types, such as bow spring centralizers and solid (rigid) centralizers, are received onto the casing to center casing in the borehole and to provide the desired radial spacing (“stand-off”) of the casing from the wall of the borehole.

FIG. 1 is an elevation view of a tubular assembly 2 having a centralizer 5 positioned on a casing segment 7 between two conventional stop collars 6. The centralizer 5 includes a plurality of ribs 4 secured to a sleeve 3. The sleeve 3 of the centralizer 5 is slidably received on the casing segment 7 to provide stand-off between the casing and the borehole (not shown).

The stop collars 6 may be slidably received onto the casing segment 7 and secured with set screws 9. The centralizer 5 is axially movable along the casing segment 7 between the opposed stop collars 6. One of the stop collars 6 limits movement of the centralize 5 in one axial direction, and the other limits movement of the centralizer 5 in the other axial direction. The separation 8 between the stop collars 6 is selected according to the desired degree of allowable movement for the centralizer 5. Very little or no movement of the centralizer 5 is often preferred, in which case the stop collars 6 may be installed directly abutting the centralizer 5.

Set screws used to secure conventional stop collars to a casing segment or other tubular member generally include elongate threaded shafts for mating with threaded holes along the stop collar. The set screws are threadedly rotated to forcibly engage an outer wall of the casing. With sufficient rotation, the set screws may “bite” into the outer wall of the casing to more thoroughly secure the stop collar. Several set screws are typically needed to sufficiently secure the stop collar under the forces it may encounter as the casing string is moved in the borehole.

Even when set screws are properly tightened, centralizers may engage borehole restrictions, irregularities, or other obstructions with forces large enough to move the centralizer off its set position on the casing string. Set screws may perform poorly under certain circumstances, such as when used on pipe made of very hard metal. The hardness may prevent the set screws from sufficiently biting into the pipe to secure the stop collar. Set screws have other shortcomings as the diameter of the casing increases because of variations in standard casing diameter. These variations, which are acceptable within a certain range, substantially increase the likelihood of a loose fit between the stop collar and the casing. A stop collar having a loose fit may require repositioning or rotation on the casing segment to ensure that the set screw will contact and bite into the wall of the casing upon rotation of the set screw. However, elastic deformation of stop collars is greater with large diameter sleeves, and full deployment of the set screw may not provide sufficient maintained contact with the casing to reliably secure the centralizer at the selected position.

What is needed is a stop collar that can be reliably secured in place on a segment of casing to prevent unwanted movement of a centralizer along the length of the casing. What is also needed is a method of securing a stop collar that promotes uniform casing stand-off and favorable cement placement by preventing centralizer movement during casing string installation.

SUMMARY OF THE INVENTION

According to one embodiment of a method of present invention, a pair of web collars each having a plurality of circumferentially disposed apertures are positioned on a tubular member adjacent the opposite ends of a centralizer. At least one threaded member is threaded through the web collar to frictionally engage the tubular member. Uncured epoxy is disposed into at least some of the plurality of apertures, and the epoxy cures to bond with the tubular member to secure the centralizer in place. The web collars are configured for limiting axial movement of the centralizer along the tubular member. The uncured epoxy may be applied by hand to the web collar with an implement, such as a putty knife. Other implements may be optionally used to apply the epoxy. The web collar may be formed by perforating a sheet of material to form a web. The web may be bent to position opposing ends in proximity to one another. A seam between the opposing ends may be joined to create a sleeve.

In a second embodiment of the web collar of the present invention, the web collar comprises a sleeve having a bore and a plurality of circumferentially disposed apertures. The stop collar is configured for being positioned on the tubular member. A plurality of epoxy deposits are disposed within the apertures. The epoxy deposits bond to the tubular member, interior to the apertures, to secure the web collar to the tubular member. The apparatus may include at least one set screw, and the web collar may have one or more radial holes for threadably receiving the one or more set screws. The plurality of apertures may occupy at least 50% of the surface area of the web collar. The internal diameter of the web collar may be slightly larger than the external diameter of the tubular member.

In a third embodiment, a kit is provided for centering a tubular member within a borehole. The kit includes a web collar having a plurality of circumferentially disposed apertures, wherein the web collar is configured for receiving the tubular member. A quantity of curable resin may be supplied, along with an optional implement for applying the curable resin to the plurality of apertures. At least one threaded member may be supplied as well, configured for passing through a wall of the web collar to frictionally engage the tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art centralizer secured in place on a casing segment using a pair of stop collars.

FIG. 2 is a perspective view of one embodiment of the web collar according to the present invention, having generally rectangular apertures.

FIG. 3 is a perspective view of a second embodiment of the web collar according to the present invention having generally circular apertures.

FIG. 4 is a perspective view of a web collar being installed on a casing segment for limiting axial movement of a centralizer.

FIG. 5 is a flowchart illustrating a method of installing a web collar on a casing segment according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, an apparatus is provided for effectively and reliably limiting axial movement of a centralizer on a tubular member. A web collar is a sleeve having a plurality of strategically sized and positioned apertures. The apertures are positioned on the sleeve to form a web. The apertures of the web are adapted for receiving and retaining a viscous epoxy until it cures. Once the epoxy has cured, a strong bond is formed between the epoxy and the tubular member on which it is received. One or more set screws may be provided to secure the web collar on the tubular member until the epoxy has cured.

In another embodiment, a method is provided for securing a web collar to a tubular member, to effectively and reliably limit axial movement of a centralizer. In one embodiment of the method, a plurality of apertures is formed in a sleeve. The apertures may occupy a large percentage of the circumferential surface area of the collar, for the epoxy to contact and adhere to a large surface area of the outer wall of the tubular member. The epoxy may be applied by hand, such as by using a putty knife, to substantially fill all or a substantial portion of the apertures. Prior to applying the epoxy, one or more set screws may be threaded into the collar to forcibly, frictionally engage the outer wall of the tubular member.

In yet another aspect, the web collar, epoxy, implement for applying the epoxy, and optional set screws, may be provided as a kit. For example, a web collar may be packaged and sold with a container of two-part epoxy, where one part is a resin and the other part an active agent to be added to the resin. The kit may include one or more implements, such as a putty knife. The type and quantity of resin, as well as the type and size of the implements, may be selected according to such factors as the size of the web collar, the percent surface area occupied by the apertures, the type of tubular member, and the type of environment in which the kit is to be used.

A variety of resin or other adhesive materials may be selected for securing the web collar on the tubular member. The term “resin” includes any of a variety of viscous, flowable adhesive materials that may be cured or otherwise hardened, usually upon addition of a hardener or agent. Epoxy is a common type of resin-based adhesive discussed in connection with the embodiments shown in the figures. Other resins or flowable adhesives may alternatively be used in one or more other embodiments.

The web may be formed from a sheet of metal in which apertures are more easily mechanically stamped, drilled, cut, or otherwise formed. The web may then be rolled or formed to join opposing ends in the general shape of a sleeve to form a web collar. A seam between the opposing ends may be welded or otherwise fastened.

An alternative method of forming the web collar may include cutting a section from a tube of the desired diameter and thickness to form a sleeve. The apertures may be subsequently formed by laser-cutting. Alternatively, the web collar may be formed by cutting a section of perforated tubing, wherein the size and position of perforations of the perforated tubing are strategically selected according to considerations set forth herein.

The apertures may serve an additional function of controlling the flow of viscous epoxy in and around the apertures. It is desirable for the epoxy to remain within the apertures. In some embodiments, the size, shape, positioning, and/or number of apertures may be selected to control the retention of epoxy while the epoxy is curing. For example, some embodiments may have a greater number of apertures than in other embodiments, to increase retention of epoxy. The percentage of surface area that the apertures occupy may optionally be controlled according to the size, number, spacing, and positioning of the apertures.

FIG. 2 is a perspective view of a web collar generally indicated at 10. The web collar 10 has a plurality of generally rectangular apertures 12 formed therein. The apertures 12 are positioned and spaced to define a web 14. The web 14 includes a plurality of intermediate portions 16 interconnected by outer portions 18. The apertures 12 occupy a substantial percentage of an outer surface of the web collar 10. In other embodiments, the apertures 12 may be further increased in size or decreased in spacing so that the apertures 12 occupy an even greater percentage of the outer surface 20. An interior surface 11 of the apertures 12 provides additional bonding area and helps retain epoxy subsequently disposed in the apertures 12. Threaded holes 22 are optionally provided for receiving set screws to secure the web collar in place on the tubular member during application and curing of the epoxy.

FIG. 3 is a perspective view of another embodiment of a web collar generally indicated at 30. The web collar 30 has a plurality of generally circular apertures 32 formed therein. The apertures 32 are positioned and spaced to define a web 34. The web 34 includes a plurality of intermediate portions 36 interconnected by outer portions 38. The apertures 32 occupy a substantial percentage of an outer surface of the web collar 30. An interior surface 31 of the apertures 32 provides additional bonding area and helps retain epoxy subsequently disposed in the apertures 32. Threaded holes 42 are optionally provided for receiving set screws to secure the web collar in place on the tubular member during application and curing of the epoxy.

FIG. 4 is a perspective view of a web collar 62 having a plurality of apertures 74 secured to a casing segment 64. The web collar 62 may be positioned on the casing segment 64 by sliding the web collar 62 over an end 72 of the casing segment 64. The casing segment 64 may be supported horizontally on a rack (not shown). A set screw 70 is threaded through the web collar 62 into engagement with the casing segment 64 to secure the web collar 62. The set screw 70 is recessed to avoid interference with any external objects when the web collar 62 is subsequently secured on a casing string and lowered into a well.

The web collar 62 may be packaged and sold as a kit together with an epoxy container 78, a patty knife 88, and optional set screws 70. The putty knife 88 or other implement may be used to apply the epoxy 78 by hand to fill the apertures 74 with epoxy deposits 76. With the casing segment 64 positioned horizontally as shown, the epoxy may first be applied to the apertures 74 along the upper half of the web collar 62. The filled apertures may be taped off, such as with cellophane tape 80, to prevent the uncured epoxy from running out of the apertures before it is cured. After tape 80 is applied, the casing segment 64 may be rotated about its axis so unfilled apertures face upwardly. The unfilled apertures may then be filled.

The epoxy deposits 76 cure and bond to the surface 86 of the casing segment 64. The cured epoxy deposits 76 are analogous to keys welded on a shaft, in that the cured epoxy deposits or “keys” 76 retain the web collar 62 on the casing segment 64 by restricting movement of the web collar 62. The cured epoxy deposits/keys 76 may, therefore, retain the web collar 62 on the casing segment 64 even if the apertures 74 are not completely filled, and even if the epoxy deposits 76 do not bond with the interior surfaces (see elements 11 and 31 of FIGS. 2 and 3, respectively of the apertures 74. After the epoxy deposits 76 cure, the axial retention of the bonded web collar 62 is much stronger than with temporary set screws 70 alone, and much stronger than even with prior art stop collars wholly secured by set screws. The web collar 62 secured in this fashion may provide greater axial retention to a centralizer than a conventional (non-perforated) stop collar secured only with a thin layer of epoxy between the conventional stop collar and a casing segment.

The apertures 74 of the web collar 62 desirably expose a large surface area on the casing segment 64 for the epoxy 78 to bond with. In one embodiment, the interior surface 84 of the apertures 74 provides an optional, additional surface area for the epoxy adherence to increase the bonding strength between the web collar 62 and the casing segment 64. The interior surface 84 increases with increasing aperture size. Thus, the size of the apertures 74 may be selected to occupy a desired percentage of the surface area of the web collar 62 and to control the surface area exposed at interior surface 84.

An annular gap 82 between the web collar 62 and the casing segment 64 may provide another, optional bonding location for the epoxy 78 to be applied. Thus, in some embodiments, the retention provided by the epoxy deposits 76 in the apertures 74 is supplemented by providing a thin layer of epoxy to the web collar 62. The diameter of the web collar 62 used may be selected according to the size of the gap 82 desired, and the size of the gap 82 may, in turn, be selected according to the amount of epoxy desired to be applied between the web collar 62 and the casing segment 64. Alternatively, the gap 82 may be minimized to achieve a tight fit with the casing segment 64, and little or no epoxy may be provided between the collar 62 and the casing segment 64. An advantage of applying the epoxy 78 mostly or wholly within the apertures 76 is that the epoxy 78 may be more efficiently and quickly applied. Also, the epoxy 78 may be applied with simple, inexpensive, and readily-available tools, such as the putty knife 88.

In most cases, the surface 86 of the casing segment 64 must be treated or conditioned prior to applying epoxy to increase the strength of the bonding. For example, the surface 86 may be sanded, shot-peened, sand-blasted, chemically etched, or otherwise prepared, and dried to remove moisture, grease, oil or other contaminants. An interior surface of the web collar 62 may be similarly treated.

FIG. 5 is a flowchart illustrating a method of installing a web collar and centralizer on a tubular member, such as casing segment, according to one embodiment of the invention. In step 100, a user starts by selecting or identifying various parameters, such as the type of tubular member (e.g., casing, drill pipe, production pipe); the tubular member's size and material properties; the environment in which the assembly will be used, and so forth. In step 102, a user uses the information identified in step 100 to select the aperture size, shape, quantity, and the percentage of surface area to be occupied by the apertures. In step 104, the user forms the web collars by cutting the apertures from sheets and by bending and welding the sheets. In step 106, the user treats the inner surface of the web collars and the outer surface of the tubular member, and optionally the interior surface of the apertures, to increase bonding surface area or otherwise strengthen the bond to be formed with the epoxy. In step 108, the user positions the web collar on the tubular member. In step 110, the user installs and tightens the set screws to sufficiently secure the web collar to the tubular member during the subsequent procedure of applying epoxy. The user may slide the centralizer onto the tubular segment abutting the secured first web collar and repeat steps 108 and 110, positioning the second web collar abutting the other end of the centralizer and tightening the set screws.

After forming and positioning the web collars and installing the set screws, the user secures each web collar to the tubular member with epoxy, as follows. In step 112, the user mixes the epoxy or other flowable adhesive, if necessary. In step 114, the user applies the epoxy with putty knife or other implement to apertures in the web collars. With the tubular member horizontally positioned in a stand, the user may apply epoxy to apertures at the upwardly disposed portions of the web collars. Then the user may tape off those apertures, and rotate the tubular member to position the remaining apertures. In step 116, the user waits for a period of time for the epoxy to cure. Curing time may vary with brand, type, and so forth. The manufacturer of the epoxy may provide suggested curing times and other information regarding its use. In step 118, if the resin has cured, the user may advance to step 120, wherein the assembly is ready for use. For example, the assembly may be positioned downhole in a tubular string.

Embodiments of the invention effectively and reliably limit axial movement of a centralizer on a tubular member. The web collar provides a large amount of surface area for epoxy bonding, both on the web collar and on the tubular member. The size of the apertures may be selected to optimize these benefits. The apertures further provide a reliable way to bond the web collar. The epoxy may be applied by hand using common implements such as a putty knife. No special implements are required to inject epoxy between the web collar and the tubular member. Furthermore, the web collar may be quickly positioned and held in place with a minimal number of set screws. The reliability provided by embodiments of the invention further enhances efficiency and lowers cost by minimizing downtime, as compared with known methods of securing a conventional stop collar. Many other features and advantages will be apparent to those skilled in the art. However, the advantages mentioned are not intended to limit the scope of the invention.

The terms “comprising,” “including,” and “having,” as used in the claims and specification herein, shall be considered as indicating an open group that may include other elements not specified. The terms “a,” “an,” and the singular forms of words shall be taken to include the plural form of the same words, such that the terms mean that one or more of something is provided. The term “one” or “single” may be used to indicate that one and only one of something is intended. Similarly, other specific integer values, such as “two,” may be used when a specific number of things is intended. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

1. A method, comprising: positioning a web collar on a tubular member, the web collar having a plurality of circumferentially disposed apertures; threading at least one threaded member through the web collar to frictionally engage the tubular member; disposing an uncured epoxy into selected apertures; and curing the epoxy to bond with the tubular member.
 2. The method of claim 1, comprising: disposing a centralizer on the tubular member adjacent to the web collar; wherein the web collar is configured for limiting axial movement of the centralizer along the tubular member.
 3. The method of claim 1, wherein the step of disposing uncured epoxy into the apertures comprises applying epoxy with an implement, by hand.
 4. The method of claim 3, wherein the implement is a putty knife.
 5. The method of claim 1, further comprising: taping off the selected apertures.
 6. The method of claim 5, further comprising: disposing uncured epoxy into other apertures of the web collar; and disposing uncured epoxy into other apertures.
 7. The method of claim 1, further comprising: forming the stop collar by perforating a sheet of material to form a web, bending the web to position opposing ends in proximity to one another, and joining a seam between the opposing ends.
 8. An apparatus, comprising: a tubular member; a web collar disposal on a tubular member, the web collar having a bore for being received on the tubular member, and a plurality of circumferentially disposed apertures; a plurality of epoxy deposits each disposed within a respective one of the apertures, the epoxy deposits being bonded to the tubular member interior to the apertures, to secure the web collar to the tubular member; and a centralizer disposed adjacent to stop collar, wherein the web collar is configured for limiting axial movement of the centralizer along the tubular member.
 9. The apparatus of claim 8, wherein the at least one threaded member comprises a set screw, and wherein the web collar has one or more radial holes for threadably receiving the one or more set screws.
 10. The apparatus of claim 8, wherein the plurality of apertures occupies at least 50% of the surface area of the web collar.
 11. The apparatus of claim 8, wherein the internal diameter of the web collar is slightly larger than the external diameter of the tubular member.
 12. A kit for spacing a tubular member within a borehole, comprising: a web collar having a plurality of circumferentially disposed apertures and a bore for receiving the tubular member; a quantity of curable resin; and an implement for applying the curable resin to the plurality of apertures.
 13. The kit of claim 12, further comprising: at least one threaded member configured for passing through a wall of the web collar to frictionally engage the tubular member. 